<template>
  <header class="header">
    <h1>todos</h1>
    <input id="toggle-all" class="toggle-all" type="checkbox" >
    <label for="toggle-all"></label>
    <input
     v-model.trim="taskName"
     @keyup.enter="add"
      class="new-todo"
      placeholder="输入任务名称-回车确认"
      autofocus
    />
  </header>
</template>

<script>
export default {
 data(){
   return {
     taskName:''
   }
 },
 methods:{
   add(){
     if(this.taskName.length===0){ return alert('任务名不能为空！')}
     this.$emit('taskName',this.taskName)
   }
 }
}
</script>